JPH0677083B2 - Method for manufacturing color filter - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a method for manufacturing a color filter, and more particularly to an improvement in a step of forming a high-definition color filter on a solid-state image sensor.

[Prior art and its problems]

As a method of forming a color filter on a solid-state imaging device, a conventional dyeable resist is provided on the same device, exposed and developed to pattern a desired dyeing area, and then the patterned area is dyed using various dyeings. A so-called "dyeing method" for forming a filter layer is known. In this dyeing method, the main purpose is to improve the pattern shape of the dyeing area and to stabilize the reproduction of spectral characteristics by making the dyeing layer uniform in thickness, in order to avoid the effects of unevenness on the surface of the solid-state image sensor before forming the dyeing layer. A transparent smoothing layer is often provided.

Polysilicon or silicon nitride film is usually formed on the surface of a solid-state image sensor such as a CCD so as to cover the upper layer of an aluminum wiring pattern, and the width of the unevenness is about 1.5 to 4 μm. Patterning and resolution will be significantly reduced if a resist to be a dyeing layer is directly provided and patterned, and there are many variations in spectral sensitivity after dyeing.
The characteristics of the image pickup device are remarkably poor. Therefore, the provision of the smoothing layer as described above is an extremely important step in the method of forming a color filter on a solid-state image sensor.

Conventionally, as a method for providing such a smoothing layer, for example, a vinyl cinnamate resist or a rubber resist containing a photosensitizer is provided on the device by spin coating, and exposed and crosslinked. However, in this method, the resist film thickness that can be uniformly coated by one spin coating is at most about 2 μm, and even if a thin smoothing layer is provided to this extent, the influence of the unevenness of the surface of the solid-state imaging device is still large. Surface flattening was not fully achieved. It has also been attempted to stack these resists twice or several times by spin coating to provide a thick film sufficient for planarization, but this is absorbed in the depth direction of the substrate due to the photosensitive groups in the resist. Since the light intensity decreases, uniform exposure cannot be performed, and as a result, the resist is cross-linked only unevenly. Therefore, even when the smoothing layer is patterned as needed, or when the resist that becomes the dyeing layer is patterned thereafter, even the smoothing layer in the exposed portion is partially dissolved in the developing solution. However, there has been a problem that the residual film ratio of the smoothing layer with respect to the initial film thickness is low, and a thick film sufficient for flattening cannot be obtained.

Alternatively, a method of improving and designing the structure of the element itself so as to be as flat as possible can be adopted, but this requires a large modification of the manufacturing process to achieve the specification of the element characteristics, and is not easy.

In recent years, as the demand for miniaturization, high performance, and high definition of solid-state imaging devices has further increased, further improvement has been demanded for miniaturization of color filter pixel size, uniformity of spectral characteristics, and stability of color filter surface removal. Came to be. At this time, the step of smoothing the element substrate is more important than ever, and it is necessary to optimize it so as to cope with the above trend. That is, in the smoothing layer forming step,
At least transparent (95% transmittance in the 400-800 nm wavelength range)
Above, flatness (~ 4μm unevenness of the element surface 0.2μm
It is necessary to establish the selection of materials and processes that can sufficiently achieve (~ 0.5 μm).

[Object of the Invention]

The present invention solves the conventional problems relating to the smoothing of the surface of a solid-state imaging device substrate that is adopted when forming a color filter by such a "dyeing method", and provides a method for producing a highly accurate color filter advantageously in mass production. The purpose is to do.

[Summary of the Invention] In order to achieve the above object, the present invention provides a negative-type resist having a different photosensitive group concentration in sequence on a solid-state imaging device when forming a smoothing layer on the substrate, and then the resist layer is formed. The main purpose is to expose and crosslink to flatten the element. That is, the present invention utilizes the fact that the exposure and development characteristics of the negative resist remarkably differ depending on the concentration of the photosensitive group, and the smoothing resist layer having a high photosensitive group concentration is first provided on the element substrate, and then the resist having a low photosensitive group concentration is used. This creates a concentration gradient of the photosensitive group in the depth direction of the smoothing layer to induce exposure cross-linking according to this gradient, and to provide a flat resin layer on the element, which is extremely easy. By smoothing the element substrate, a high-definition color filter can be manufactured.

Hereinafter, the present invention will be described in detail with reference to the drawings.

As shown in FIG. 1, the solid-state image sensor is entirely covered with polysilicon or silicon nitride (13) except for the aluminum pad area.

The step difference in the substrate is usually 3 to 4 μm. In the conventional method, even if a strong smoothing layer (17) is provided on the unevenness of the step, the thickness is about 2 μm in the concave part of the step, and the element is not sufficiently flattened. For this reason, if dyeing pattern layers such as cyan (14) or yellow (16) are sequentially provided on the smoothing layer through the intermediate layer (15), the thickness of the dyeing layer is not even within one pixel area as shown in FIG. It is uniform and the degree of variation in film thickness is 0 even on the entire surface of the solid-state element substrate.
It reaches 7 to 1.2 μm. The spectral characteristics of the dyed layer required to realize a high-definition color filter are, for example, within ± 5% of the specifications of the set transmittance at the observation wavelengths of 500 nm and 570 nm for the complementary color filters, dian and yellow, respectively. It has to be controlled by.

In order to realize this, it is necessary to keep the variation in film thickness of the dyed layer within ± 0.3 μm at maximum, as shown in FIG. Second
As shown in the figure, it can be said that the above-mentioned object cannot be achieved at all in the conventional method because the planarization is not sufficiently achieved.

An example of application of the present invention is shown in FIG.

Smoothing layer (resist with high photosensitive group concentration) 17 on the solid element substrate
Is first formed, and then a smoothing layer (low photosensitive group concentration resist) 17 'having a different photosensitive group concentration is provided. Since smoothing is sufficiently achieved, if necessary, a resist having a lower photosensitive group concentration can be laminated.

When these smoothing layers (17) and (17 ') are simultaneously exposed with a predetermined exposure amount, a cross-linking residual film is formed according to their exposure and development characteristics. At this time, not only the upper smoothing layer (17) whose surface is directly exposed, but the lower layer light absorption is small, and thus light of sufficient energy is absorbed. As a result, the cross-linking of the resist progresses sufficiently in both the smoothing layers (17) and (17 '), so that the residual film rate relative to the initial film thickness even when exposed to a developing solution when the dyeing pattern layer is provided, for example. However, it is possible to obtain a smoothing layer having a desired thickness and a very large flatness. When the cyan and yellow layers are formed on such a smoothed layer as in the conventional example, there is no influence of the step difference and the unevenness of the underlying layer, so that a filter pixel having extremely excellent film thickness and dyeing uniformity can be formed.

The negative type resist applicable to the formation of the smoothing layer of the present invention includes cyclized isoprene, butadiene and other rubber-based rubber compounds and various azide compounds such as 3,3'-dimethoxy-4,4 'as a photosensitizer.
-Diaddiphenyl, 4'-methoxy-4-azidophenylmine, 44'-diazidodiphenylamine, 4,4'-
Diazidodiphenylnutane, 1-azidobylene, 3,3 '
-Dimethyl-4,4'-diazidophenyl, 4,4'-diazidobenzophenone, 4,4'-diazidostilbene, 4,4 '
-Diazidochalcone, 2,6-di- (4'-acidbenzal) cyclohexanone 2,6-di- (4'-azidobenzal) -4-methylcyclohexanone containing azido rubber negative resist or partial introduction and substitution of azido group Azide-based polymers such as polyazidobenzoic acid, vinyl azidophthalate, polyazidostyrene azidobenzaldehyde phenol, or polycinnamic acid vinyl partially having cinnamoyl groups, polycinnamylidene vinyl acetate, polyvinylcinnamate.
Examples include cinnamylidene acetate copolymerization, polyvinyl acetate / cinnamylidene acetate copolymerization polyvinylbenzoate / cinnamylidene acetate copolymerization, and the like.

When applying these negative resists to the present invention, it is important to fully understand the exposure and development characteristics depending on the concentration of the photosensitive group. For example, regarding the rubber-based resist / azide photosensitizer system mentioned above, the exposure and development characteristics of the resist change depending on the concentration of the photosensitizer added as shown in FIG. In the figure, the characteristic curve shows that the concentration of the photosensitizer decreases in the order of (1), (2), (3) and (4), and the residual film rate is 100% at the exposure amount of 10 in the case of (1), but the same exposure amount. In (3) of 30
%. Therefore, the high-concentration resist of (1) is used as the lower layer,
When the laminated system having the low-concentration resist of (3) as an upper layer is exposed with this exposure amount, a smoothing layer having a thickness of 65% of the initial film thickness is formed. The reason for forming the low-concentration resist in the upper layer is to prevent the light absorption from being significantly attenuated in the depth direction of the thick resist coated on the step portion.
Many negative resists are used by adding various sensitizers for the purpose of improving spectral sensitivity. Also in the method of the present invention, these uses are not limited,
Usually, these sensitizers strongly absorb the photosensitizing wavelength. Therefore, when added to the resist material provided in the upper layer in particular, a significant light attenuation is caused, and in a range that does not reduce the photosensitive crosslinking of the lower layer resist. It is desirable to select.

The color filter to which the method of the present invention is applied is coated with a negative resist having a dyeability, such as gelatin or casein to which ammonium dichromate is added, on a solid-state image sensor smoothed by the above-mentioned method to form a predetermined pattern. It is carried out by exposing and developing through a mask having a dye, immersing it in a dyeing solution containing an appropriate dye for dyeing and coloring, and repeating this several times.

〔The invention's effect〕

The flatness of the solid-state imaging device smoothed by the method of the present invention is significantly improved as compared with the conventional method, and the pattern shape resolution and the pattern shape resolution of the dyeable resist formed on the smoothed substrate are The film thickness uniformity is also very good. For this reason, it becomes possible to form a fine color filter having uniform spectral characteristics on the same element by an extremely simple method, which produces an extremely great effect on production.

Example of Invention

2,6-di- (4'-) was added to polyisoprene rubber on a CCD solid-state image sensor with a step of 3 μm covered with polysilicon.
A resist solution having a high photosensitizer concentration added with 5% of azidobenzal) -4-methylcyclohexanone was applied to a thickness of about 2 μm by spin coating. Next, a resist having a low photosensitizer concentration in which the photosensitizer of the same resist was 2% was formed to a thickness of 2 μm and laminated. Baking treatment was performed at 80 ° C. for 30 minutes, contact exposure was performed through a photomask having a predetermined pattern, and development was performed with a predetermined developing solution. When the film thickness of the step portion was measured after baking, the unevenness was 0.3 μm. For comparison, when a substrate provided with a layer consisting of only one resist layer having a high photosensitizer concentration was examined, the step difference was about 1.2 μm.

An ammonium dichromate / casein resist having a thickness of 1 μm was provided on the smoothed CCD elements, and pattern exposure was performed in a filter pixel shape to examine the shape and film thickness of the resist pattern. In the case of the substrate smoothed by the method of the present invention, the film thickness of the resist pattern cross section observed by the scanning electron microscope was extremely uniform, and the resist film thickness difference was within 0.2 μm even in the concave portion. On the other hand, in the substrate according to the conventional method, the film thickness difference of 0.8 μm still occurred at the upper and lower portions of the step. After cyan dyeing, an intermediate layer (FSR manufactured by Fuji Yakuhin Co., Ltd.) was provided, a yellow dyeing layer of casein was formed in the same manner as above, and a color filter was provided on the CCD.

Comparing the spectral characteristics of the devices, it was found that those formed by the method of the present invention had extremely uniform and good color separation and color tone.

[Brief description of drawings]

FIG. 1 is a sectional view of a CCD solid-state imaging device, FIG. 2 is a sectional view of a color filter layer on a CCD formed by a conventional smoothing method, and FIG. 3 is a color filter on a CCD according to the present invention. FIG. 4 is a cross-sectional view showing the relationship between the resist film thickness and spectral characteristics (absorption rate), and FIG. 5 is a view showing the dependence of the exposure characteristics of the resist on the photosensitive group concentration. In the figure, 10 ... Base, 11 ... Photosensor area, 12 ... Wiring Al, 13 ...
Polysilicon layer, 14 ... First dyed layer, 15 ... Intermediate layer, 16 ... Second dyed layer, 17, 17 '... Smoothing layer. a ... Optimal range of spectral characteristics, b ... Set film thickness range

Claims (2)

[Claims] 1. A method of manufacturing a color filter in which a color filter layer is directly laminated on a solid-state image sensor,
Prior to the step of providing a colored layer on the element substrate, a step of smoothing unevenness on the element substrate surface by sequentially stacking negative resists having different photosensitive group concentrations on the element substrate in order of increasing photosensitive group concentration A method for manufacturing a color filter, comprising: 2. A negative resist is at least one selected from the group consisting of isoprene, a system containing an azide compound as a photosensitizer in butadiene rubber, an azide polymer, and a vinyl polymer containing a cinnamoyl group. A method of manufacturing a color filter according to claim 1.